The present invention pertains to the field of analyte detection and, more specifically, to an automated system and method for the use of fluorimetric and colorimetric detection inks and capillary action to detect one or more target analytes, including explosives, narcotics, organophosphates, gunshot residue and toxic industrial chemicals.
The detection of small amounts of explosives is important for the prevention of terrorist attacks and for the safeguarding of civilians, military personnel and bases, airports and other transportation locations, and tourist and commercial venues. The low volatility of many explosives, such as TNT, RDX, and PETN, makes vapor sampling difficult and largely inefficient, especially at low temperatures. Thus, efficient solid-state sampling techniques are desirable for many applications. Chemical sensors are often desired because they are able to detect trace amounts of explosives and can be packaged into simple-to-use, low-cost devices. Conventional detection methods, such as X-ray diffraction, nuclear quadrupole resonance, and gas chromatography-mass spectrometry, though highly sensitive, are expensive, difficult to maintain, susceptible to false-positives, and are not easily manufactured into low power, portable devices. Low end systems, while physically simple compared to the high end systems, require more complex user interaction and interpretation.
A major source of terrorist funding is gained through narcotics trafficking. This relationship implies that there could be a correlation between narcotics and terrorist weapons, including explosives. Therefore, the ability to detect narcotics concurrently with explosives may potentially be valuable in fighting the terrorist network at large. In addition to the international needs, narcotics detection is also a focus for other domestic criminal and forensic applications. Narcotics of particular interest are heroin, cocaine, marijuana, and methamphetamines. Analytical instrumentation, such as FT-IR, Raman, GC-MS, and IMS, may be used to identify specific drugs, but these are typically ill-suited for widespread field use because of their size and/or expense. Existing colorimetric detection technology employed in presumptive forensic field-test kits is used to detect visible quantities of narcotics that are typically low milligram quantities. Many of these kits require sampling and dispensing an amount of one or more solutions into a reservoir, visually interpreting a color change, and referencing a color chart to look for a specific color while discounting other colors. This process can be time consuming, subject to bias in an individual's perception of color. The overall performance is subject to change based on an individual's eye sight and external lighting conditions. Automating the detection of these colorimetric kits would at least remove the subjectivity in detection and performance dependency on external lighting conditions.
Like narcotics, gunshot residue (GSR) is an important analyte of interest for both domestic and international operations. Colorimetric kits exist for GSR detection, most of which rely on detection of post-blast nitrate and nitrite residue, and the signal degrades rapidly after firing. Field samples most often represent metal particles collected from a primer and sent to a lab for analysis, typically by a scanning electron microscope (SEM); results are often not available for weeks. A rapid and reliable field test would yield information immediately to assist law enforcement in their duties.
A multi-assay tool capable of detecting explosives, narcotics, and GSR in a single instrument and correlating this data would be a valuable tool in combating terrorist and criminal activities, both domestically and internationally. Optimization of such a tool for widespread use would require simplicity of use, portability, low power and maintenance requirements to be incorporated in a low cost device. Additional advantages would be gained by minimizing user interactions, particularly the number of analysis steps and ambiguity in user interpretation. Importantly, such an automated tool would allow for greater sensitivity and eliminated dependency on external lighting conditions and viewer's eyesight.